<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<link rel="stylesheet" href="mystyle.css"/>
<script src="my.js"></script>
<body>

<div>
    <button type="button" onclick="area_of_circle(3,3.14)">定义函数，计算圆面积</button>
    <p id="area"></p>
</div>
</body>
</html>